Original URL: http://www.theregister.co.uk/2005/05/05/exoplanet_confirmed/

Smudgy blur is an exoplanet

Cool

By Lucy Sherriff

Posted in Science, 5th May 2005 12:27 GMT

Astronomers have confirmed that a candidate extra-solar planet in orbit around a brown dwarf is indeed what it appears to be: the first directly imaged planet outside our solar system.

Known as 2M1207b, the planet is approximately five times the mass of Jupiter, and is located around 200 light years from Earth in the Southern constellation, Hydra. It was seen last September as a faint dot of light in the vicinity of a brown dwarf, or failed star. However, astronomers could not rule out the possibility that it was a background object, not actually associated with the brown dwarf in any way.

Hubble's artificial-colour view of the brown dwarf and confirmed giant planet companion

In February and March of this year, the astronomers took new images of the young brown dwarf and its giant planet companion with the NACO instrument on European Southern Observatory's Very Large Telescope in northern Chile.

The new data revealed that the planet is more than 100 times fainter than the brown dwarf, 2M1207A. Its spectrum presents a strong signature of water molecules, confirming that it must be cold.

Observers had originally calculated that the probability of the two bodies being gravitationally bound at just over 99 per cent. In astrophysical parlance, this level of probability is known as 2.6 sigma, and according to some, was not really good enough to be sure. The new observations have raised this figure to 3.8 sigma, according to Glenn Schneider of the University of Arizona.

"The significance of this improvement, along with our new NICMOS observations of 2M1207A/b, presented at the Decade of Extrasolar Planets meeting at STScI in Baltimore, unequivocally demonstrate the common proper motions of 2M1207A/b," he told The Register.

"The system, with a likely mass ratio of only approximately (5-10):1 challenges, and will provide important constraints on, the current competing theories of the formation and evolution of extrasolar giant planets," he added. ®

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